Biology > Topic 8 > Flashcards

Topic 8 Flashcards

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1
Q

Isolating target gene stages

A

1) restriction enzymes
2) reverse transcription
3) artificial synthesis gene

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2
Q

Isolating target genes - restriction enzymes

A
  • DNA contains palindromic sites
  • restriction enzymes cut DNA at specific palindromic sites called restriction sites
  • if theres a restriction site either side of target gene
  • restriction enzymes can be use to cut it out
  • using restriction enzymes leaves DNA with sticky ends
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3
Q

Isolating target genes - reverse transcriptase

A
  • cells only have 2 copies of each gene (in the nucleus), it is hard to access
  • enzyme that does transcription backwards
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4
Q

Isolating target genes - artificial synthesise gene

A
  • use a ‘gene machine’ to make DNA from scratch
  • join about 25 nucleotides together at once
  • forms an oligonucleotide
  • join oligonucleotides together to form a synthetic gene
  • design your own gene
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5
Q

Inserting target gene stages

A

1) isolating target gene
2) insert gene into a vector
3) insert vector into bacteria

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6
Q

Inserting target genes - isolating target gene

A
  • through a: gee machine, reverse transcriptase, restriction enzymes
  • needed to add: a promoter region, terminator region, sticky ends, marker gene
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7
Q

Inserting target genes - insert gene into a vector

A
  • use the same restriction enzymes to cut plasmid (sticky ends are complementary
  • DNA ligase reform the phosphodiester bonds
  • forms recombinant DNA
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8
Q

Vector

A

Something that’s used to move DNA from one place to another

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9
Q

Recombinant DNA

A

DNA from more than one source/ organism

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10
Q

Inserting target genes - insert vector into bacteria

A
  • transgenic organism - contains recombinant DNA
  • ice cold calcium chloride
  • heat shock (increases permeability of bacterial cell wall)
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11
Q

Marker genes

A

Genes that are paired with target genes to check if the vector has been inserted properly

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12
Q

Process of marker genes

A
  • vector are often not take up by bacteria
  • to tell which bacteria transformed you need marker gene
  • transformed bacteria contains the recombinant DNA (target + marker gene)
  • Marker genes can be easily identified
  • only bacteria that have accepted the vector (transgenic bacteria) are selected and cultured
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13
Q

UV fluorescence as marker genes

A

Will fluoresce under UV

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14
Q

Antibiotic resistance as a marker gene

A

Will be able to survive in a culture with antibiotic

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15
Q

What is the use of PCR

A
  • used to amplify DNA

- sometimes called in vitro DNA amplification

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16
Q

What is needed for PCR

A
  • DNA sample
  • free DNA nucleotides
  • primers (need to select which part of DNA is copied)
  • DNA polymerase
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17
Q

What are primers

A

Short sequences of DNA that are complementary to the start of DNA sample

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18
Q

Steps of PCR

A

1) heat to 95C
2) cool to 50C
3) heat to 70C (allows rate of reaction to happen fast)
4) repeat

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19
Q

Why do you heat up to 95C for PCR

A
  • break H bonds

- Make DNA single stranded

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20
Q

Why do you cool sample to 50C in PCR

A
  • allows primers to bind
  • complementary base pairing
  • DNA double stranded
  • DNA polymerase can bind
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21
Q

Why do you heat sample to 70C in PCR

A
  • DNA polymerase adds complementary nucleotides

- forms phosphodiester bonds

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22
Q

Why do you repeat the PCR method

A

each cycle we double the DNA

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23
Q

Summary of gene technology stages

A

1) isolate target gene
2) insert gene into vector
3) insert vector into bacteria
4) identify transgenic organism
5) culture transgenic bacteria
6) extract + purify protein

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24
Q

What do you use to isolate target gene

A
  • restriction enzymes

- (gene machine, reverse transcription, promoter + terminator)

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25
What is used to insert a gee into a vector
- same restriction enzyme - sticky ends to be complementary - DNA ligase
26
What is used to insert vector into a bacteria
- recombinant DNA | - Ice cold CaCl2 + Heatshock
27
What is used to identify transgenic organisms
- marker gene | - U.V. Fluorescence/ radioactivity/ antibiotic resistance
28
What is used to culture transgenic bacteria
- transcribe + translate recombinant DNA | - Make the protein of target gene
29
Gene therapy
Changing faulty alleles that cause genetic disease
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Gene therapy for dominant alleles
- sufferer will be heterozygous - they will have the functional allele - silence dominant allele - use a vector to add a DNA fragment into dominant allele - dominant allele won’t be transcribed - recessive allele expressed
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Gene therapy for recessive alleles
- sufferer will be homozygous - use a vector to add the functional allele to DNA - dominant allele will be expressed
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Possible problems with gene therapy
- allele insert into wrong locus - could silence wrong gene by mistake - Gene could be over expressed - use of gene therapy could be used for non-medical uses
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Germ line gene therapy
Change the allele of gametes
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Inheritance from germ line gene therapy
- all future offspring inherit | - illegal in humans
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Somatic gene therapy
Changing the alleles of body cells (non gametes)
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Inheritance from somatic gene therapy
Offspring do not inherit change
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Mutation
A change to the nucleotide sequence of DNA
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Mutagenic agent
Increase the rate of mutations
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Base analogs
A chemical that can substitute from a normal nucleotide base
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Radiation
Change the structure of DNA
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Change DNA bases
Chemicals that react with DNA to change its structure
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Substitution
One base is swapped for another | - no change, single amino acid changed
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Addition
An extra base is added
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Deletion
A base is removed | - frame shift, all the following triplets in the sequence will be affected
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Inversion
A sequence of bases is reverse | - no change, change a few amino acids, no frame shift
46
Duplication
One or more bases are repeated
47
Translocation
A sequence of DNA is removed from one part of the genome and moved to another part of the genome
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Changes to the base sequence of DNA
- no change to amino acid sequence - change to a single amino acid - change to sequence of many amino acids
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Why is there no change to amino acid sequence after a mutation
- amino acids are coded for by more than one triplet on DNA | - it is degenerate
50
Why is there only change to a single amino acid after a mutation
- changes to one DNA triplet - changes the translation of one amino acid - changes primary structure of the protein - change the hydrogen/ ionic bonding - change the tertiary structure of the protein
51
Why is there a change to the sequence of many amino acids
- frame shift changes the sequence of all the following DNA triplets - change all the following amino acids in sequence - changes the primary structure - changes the hydrogen/ ionic bonding - change tertiary structure
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Stem cells
Can divide and differentiate to become different types of cell
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Totipotet
Stem cells that can differentiate into any type of specialised cell
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Where are totipotent cells from
- early mammalian embryos | - can form placental cells
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Pluripotent
Stem cells that can differentiate into many types of specialised
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Where are pluripotent stem cells from
- embryos | - can’t make placental cells
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Multipotent
Stem cells that can differentiate into a few types of specialised cells
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Example of multipoint cells
bone marrow to RBC and WBC
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Unipotent
Stem cells that can differentiate into one type of specialised cell
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Example of unipotent cells
Heart unipotent cells can make cardiomycetes only
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Cell specialisation/ differentiation
- all cells contain 100% of an organisms DNA - conditions within cells control which genes are expressed into proteins - change internal environment of the cell - affect the expression of other genes (are specialised)
62
iPs cells
Treating unipotent stem cells with transcription factors that make them become pluripotent
63
How to make induced pluripotent stem cells
- use a modified virus as a vector - virus inserts transcription factor genes from pluripotent cells into the DNA of unipotent stem cells - transcription factors are expressed - ultimate goal is to make totipotent stem cells this way
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Creation of embryonic stem cells
- embryos are made in a lab by IVF - pluripotent stem cells are removed after a few days - embryo is destroyed - pluripotent stem cells can differentiate into all types of body cells
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Creation of adult stem cells
- taken from adult in an operation - adult stem cells are multipoptent - less useful for medicine as they can’t form every type of cells
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Why are stem cells used
They can differentiate to form any type of specialised cell
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Bone marrow transplants
- contains multipotent stem cells - can differentiate into RBCs and WBCs - if someone has fault bone marrow you can replace there bone marrow to form new healthy cells
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Growing new organs with stem cells
- no donors needed - iPs cells - iPs organs have the same antibodies so there is no organ rejection
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Advantages of stem cells in medicine
- saves lives - improve quality of life - prevent suffering
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Ethical issues with stem cells in medicine
- they are taken from IVF embryos which could be developed into a foetus if implanted - some people believe from fertilisation a zygote has a right to life - adult stem cells are not pluripotent - iPs cells could be the future solution
71
Transcription factors
Proteins that control the rate of protein synthesis by switching some genes on and other genes off
72
Promoter region
Short sequence of DNA at the start of a gene
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Stages of activators and repressors
1) transcription factor moves from the cytoplasm into the nucleus 2) binds to the promoter region 3) activators - help RNA polymerase to bind to DNA ( gene is transcribed) 4) repressors - prevent RNA polymerase binding to DNA (gene is not transcribed)
74
Controlling transcription factors - oestrogen
- oestrogen is a steroid hormone - oestrogen binds to a receptor called an oestrogen receptor - forms oestrogen-oestrogen receptor complex - transcription factors can also be turned on/off by second messengers
75
Cancer
Uncontrolled cell division
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How do tumour suppressor genes work
- proteins that slow down the rate of mitosis or speed up the rate of apoptosis - if theres a mutation into the tumour suppressor gene - the protein might be non-functional
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How to proto-oncogenes work
- make proteins that increase the rate of mitosis - if a proto-oncogene mutates it is called an oncogene - oncogenes can be over expressed
78
Epigenetics
Changes to gene expression caused by environmental factors
79
How does epigenetics work
- controls gene expression by preventing transcription - can be inherited between generations - helps organisms respond to changes in their environment
80
Methylation of DNA
More Methylation = Terminate Transcription - methyl can attach to DNA at CPG sites - Methylate CpG sites prevent transcription enzymes attaching - transcription is prevented
81
Affects of acetylation of histones
Less acetylation of histones Terminates Transcription
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How does the acetylation of histones work
- acetyl groups make histones space out - allows transcriptional enzymes to attach - gene is expressed - enzymes remove acetyl groups - prevents transcription
83
What does RNAi do
Controls gene expression by preventing translation
84
siRNA - small interfering RNA
- short double stranded RA - combines with proteins to form a siRNA-protein complex - siRNA is single stranded - siRNA has complementary base sequence to target mRNA - siRNA protein complex breaks down the mRNA into pieces - prevents translation - mRNA pieces are recycled
85
MicroRNA
- microRNA combines with a protein to form a microRNA-protein complex - bind to mRNA by complementary base pairing - less specific that siRNA - works on more than one mRNA - prevents translation by stopping the ribosome attatching - mRNA can be stored and used later or recycled
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Hypermethylation
Tumour suppressors genes | - means that proteins not transcribed
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Hypomethylation
Proto-oncogenes | - more protein is transcribed
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Benign tumours
- non-cancerous - grow slowly - harmless - can become malignant
89
Malignant tumours
- are cancerous - grow quickly - destroy tissue - can break up and spread in blood/ lymphatic system
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Oestrogen and breast cancer
- high levels of oestrogen can cause some types of breast cancer - oestrogen can bind to proteins to form a transcription factor called oestrogen-oestrogen receptor complex - increase rate of cell division, increase DNA replication, increase mutation, increase cancer
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Identifying tumour cells
- mitosis - more cells dividing - nuclei - large and odd shaped, more than 1 per cell - irregular cell shape - loss of normal function - disorganised arrangement
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Genome
The complete set of genetic material that an organism has
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Proteome
The complete set of protein that an organism can make
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Sequencing projects
- human genome project - sequenced whole human genome - only sequence short fragments at once - split genome up into small sections -> sequence -> put back together - sequencing methods are constantly being up dated
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Predicted amino acid sequence - simple organisms
- few regulatory genes | - little non-coding DNA
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Predicting amino acid sequence - complex organisms
- regulatory gene turns on/off other genes - lots of non-coding DNA - hard to determine proteins from DNA
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Uses of genome projects
- understanding evolutionary relatedness | - medicine - understand the antigens to develop new vaccine
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uses of genetically modified organisms in agriculture
- express protein from bacteria - protein is toxic to insects - fewer insects eat soya plants - gene from corn to rice expresses vitamin A
99
advantages of using genetically modified organisms in argiculture
- uses less chemical pesticides - more efficient food chain - prevents blindness caused by vitamin A deficiency (corn to rice gene)
100
disadvantages of using genetically modified organisms in agriculture
- monocultures have a low genetic diversity - susceptible to environmental factors eg disease - have to buy seeds every year - decrease in biodiversity
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uses of genetically modified organisms in industry and research
- making enzymes eg lipase | - transformed pathogen to TREAT disease - attach other pathogens but don't infect humans
102
advantages of using genetically modified organisms in industry and research
- reduce energy and cost - fast and cheap production - treat disease - pathogens won't develop resistance - reduce suffering
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disadvantages of using genetically modified organisms in industry and research
- could mutate and infect humans | - could be used in a negative way
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uses of genetically modified organisms in medicine
- transform bacteria to express proteins | - mammals can also be transformed to produce useful products in their milk
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advantaged of genetically modified organisms in medicine
- makes human proteins | - cheaper and easier than making protein synthetically
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disadvantages of using genetically modified organisms in medicine
- possible unexpected problems | - using animals as commodities
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DNA probes
a short sequence of DNA that is complementary to a specific allele/ mutation / gene
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uses of DNA probes
to test if a sample of DNA contains a specific sequence
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stages of using a DNA probe
1) attach a label to DNA probe 2) is sequence is present than DNA probe will hybridise and stick to DNA sample with a complementary sequence 3) rise to remove unhybridized DNA probes - DNA must be single stranded
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DNA microarray stages
1) many DNA probes attached to a tile in a grid 2) add patients DNA with label 3) DNA will hybridise to complementary DNA - 4) rinse and view labels
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How do you use DNA microarry
- attach the label to human DNA | - test multiple alleles at once
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DNA probes in genetic counselling
- used to identify: carriers of a genetic disease, specific alleles, the most effective treatment - healthcare professionals can advise people about the risks of passing on inheritable diseases, developing diseases later on in life, making informed decisions about treatment and preventions
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uses of DNA probes in genetic screening
- parents can see if they are carriers of recessive alleles | - you can diagnose and treat before symptoms show
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uses of DNA probes in personalised medicine
- if a doctor knows a patients genotype it gives the best drugs for them - change drugs if you know a patient has an allele that causes a side effect with the normal drug
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genetic fingerprinting
identifying individuals by comparing the differences in their Variable Number Tandem Repeats (VNTR)
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genetic fingerprinting in forensics
- sample of DNA from a crime scene and suspects - amplify using PCR - run gel electrophoresis - the chances of two individuals having the same number of VNTR's is very low - suspects will have more matches to the crime scene
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genetic fingerprinting for relatedness
- the more closely related two individuals are the higher the percentage match of VNTRs - conservation of endangered species to avoid inbreeding by mating individuals who are least related to help maintain genetic diversity
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genetic fingerprinting for medical diagnosis
- genetic fingerprints can be used to test for specific combinations of alleles - can be used to diagnose genetic disorders
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facts of genetic fingerprinting
- non-coding DNA contains lost of VNTRs - don't code for proteins - don't affect phenotype - vary more than coding DNA - the number of repeats of each VNTR varies
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